1. Field of the Invention
The present invention relate generally to an intramedullary implant for use in one or more bones to provide internal fixation during surgery, instrumentation for using the intramedullary implant, packaging for the intramedullary implant and the instrumentation, and also a method of implanting the intramedullary implant.
2. Description of the Related Art
Corrective surgery involving bones can include the use of external fixation devices or internal fixation devices. Internal fixation devices can be located inside the bone or outside the bone. Implants located inside bones can be referred to as intramedullary implants. Intramedullary implants can be made of metal, shape memory materials, artificial bone, or bioresorbable materials. Intramedullary implants that use shape memory materials are typically composed of shape memory materials such as Nitinol.
Intramedullary implants that are composed of Nitinol typically operate using a temperature dependent property of Nitinol called shape memory. Shape memory allows the intramedullary implants the ability to undergo deformation at one temperature and then recover their original, undeformed shape upon heating above their “transformation temperature”. In practice this is frequently accomplished by using preoperative freezing to deform the intramedullary implants from a first final shape into a second shape. After insertion the intramedullary implants recover their undeformed shape due to heating by the body above their transformation temperature. However, preoperative freezing can be a logistical challenge both to health care facilities as well as a surgeon, who has a limited amount of time to work with the implant before it warms to room temperature.
Intramedullary implants can also be designed to utilize the superelastic properties of a material such as Nitinol. In this instance, the implant deforms during implantation, but uses superelastic behavior to flex and engage the bone. A difficulty in designing a superelastic intramedullary implant is allowing the surgeon access to both sides of the implant. While it is simple to insert one side of the implant into a first bone, it becomes difficult to insert the second side into a second bone.
In designing a proper intramedullary implant that affixes one or more bones, it is also difficult to achieve proper position within the bones. In particular, when the intramedullary implant is inserted into one or more bones, one of the bones is typically less resistive to motion than the other bone due to different anatomy or bone quality. As such, when the bones are reduced or pressed together, the intramedullary implant tends to migrate in the direction of the bone that is less resistive, thereby resulting in an improper final placement of the intramedullary implant. Furthermore, once the implant is positioned inside the bone, and the bones are fully reduced so that they are touching, it is difficult to reposition the implant because there is no access to the intramedullary space.
Accordingly, an intramedullary implant design that does not require preoperative freezing and maintains the intramedullary implant in the proper position within the bones would be beneficial.